Expansion thermometer



April 13, 1943. w. NEUSE 2,316,611

EXPANSION THERMOMETER Filed Aug. 2, 1939 Patented Apr. 13, 1943 EXPANSION THERMOMETER Wilhelm Neuse, Finkenkrug, Kreis Osthavelland, Germany; vested in the Alien Property Custo-.

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Application August 2, 1939, Serial No. 287,949 In Germany September 27, 1938 1 Claim.

The present invention relates in general to thermometers of the liquid expansion type, and more in particular to thermometers of this type in which the indicating part of the thermometer is located at some distance from-the bulb or container for the main body of liquid which is subjected to the temperature changes to be indicated, the indicating device being connected with the bulb by means of a long capillary tube.

In thermometers of this type an error is introduced due to temperature changes at the capillary tube and at the indicating device, generally a Bourdon tube, which appreciably afiect the volume and pressure of the liquid. This error is accentuated if a liquid having a high coefiicient of expansion is used, because the volume of liquid in the bulb must be reduced in order to avoid excessive rise in pressure and the liquid volume in the bulb may be equal to or not greatly in excess of that contained in the capillary tube and indicating device. Thus the reading of the indicating device is not solely or even mainly dependent upon the temperature at the bulb, but is greatly affected by the temperature along the capillary tube and at the indicating device.

Efiorts have been made in the past to overcome the difficulty pointed out in the foregoing, but without success, insofar as I am aware. In accordance with any invention the problem is solved by providing a bulb or container for the main body of liquid which is of relatively large side, containing a relatively large volume of liquid having a high coefficient of expansion, and by providing means for automatically regulating the volume of liquid in the bulb in accordance with the pressure thereof, thereby preventing an excessive increase in pressure.

The invention will be described more in detail hereinafter, reference being made to the accompanying drawing, in which- Fig. 1 shows in diagrammatic form a complete thermometer constructed in accordance with the invention;

Fig. 2 shows a modification using a somewhat different form of bulb;

Fig. 3 shows a. further development of the form shown in Fig. 1; and

Fig. 4 shows an adaptation of the invention wherein it is used as a temperature regulator.

Referring to Fig. l, the reference character I indicates the bulb or container for the liquid medium 5, which is assumed to be located at the point where the temperature changes are to be ascertained. The indicating device is of known type, including a pressure responsive coil I I, and is located at a point remote from the bulb I. Connection between the bulb and indicating device is established by means of a capillary tube 2. This capillary tube may be many feet in length, as where the bulb I is located in the basement of a building while the indicating device is on an upper floor, or vice versa. The volume of liquid contained in the bulb may be, however, relatively very much greater than the volume of liquid contained in the tube 2 and in the coil II.

The means for regulating the volume of liquid in the bulb I comprises a sealed capsule 3, having corrugated walls as shown. The capsule 3 may be nearly as long as bulb I, and may be loose in the bulb or secured thereto at the lower end as shown. The capsule 3 contains a gas at atmospheric pressure and since the walls are flexible its dimensions change in response to pressure changes in the v liquid 5. A tube or sleeve 4 may be provided to prevent bending or collapse of the capsule in response to greatchanges in pressure.

The operation of the thermometer, Fig. 1, may now be briefly explained. When the temperature rises at the point where the bulb l is located, the liquid 5 expands and its pressure tends to increase. The increase in pressure is communicated along the capillary tube 2 to the coil II, by means of which the indicator is controlled. The pressure rises at a moderate rate, notwithstanding the large volume of liquid in the bulb, due to the control exercised by the capsule 3. As the pressure rises the capsule is compressed and v the volume of liquid which it displaces is reduced, thereby gradually increasing the effective volume of the bulb I. The rise in pressure is therefore a function of the resiliency of the capsule, and may have a substantially straight line characteristic over a wide range.

When the temperature is lowered at the point where the bulb is located the reverse action takes place. The liquid 5 contracts in volume and the pressure tends to fall, but the contraction in the temperature rises, the liquid !3 expands and its pressure tends to rise, but the increase in pressure is partly prevented, or is moderated, by the action of the flexible wall of the bulb, which permits the volume of liquid contained in the bulb to increase. The reverse action takes place when the temperature falls.

In Fig. 3 the bulb and capilary tube are similar to the corresponding parts in Fig. l. The capsule i5 is also substantially the same as capsule 3 in Fig. 1, but the guide sleeve i6 is enlarged and is placed outside the capsule l5 rather than inside. Surrounding the sleeve l8 there is a helical spring I, the opposite ends of which bear against the end plates 8 of capsule [5.

The operation of the modification, Fig. 3, is the same as the operation in Fig. 1, except for spring 'i, the function of which is to increase the stiffness of the corrugated Walls of the capsule l5 and thus increase its resistance to compression by the expansion of the liquid in the bulb. The liquid pressure is therefore increased. By adjusting the power of the spring, or by selecting a spring of the proper stifiness, the pressures corresponding to a given temperature rang can be raised to the desired degree.

The invention may also be employed as a temperature regulator, the pressure responsive coil M, Fig. 1, being equipped in known manner with an electrical contact or switch capable of being adjusted. Or the pressure responsive coil may be replaced by a corrugated tube 9, as shown in Fig. i. A cylindrical body H is arranged in side tube 9 in order to reduce the volume of liquid therein. Contacts H! are the usual control contacts.

When the temperature rises at the point where the bulb is located the liquid pressure rises, and the tube 9 expands lengthwise to close the contacts ill. Thus a control operation is initiated in known manner which will reduce or cut ofi the supply of heat. When the temperature falls, the liquid pressure in the bulb is reduced, the tube 9 contracts, and the contacts 10 are opened.

The invention is not limited to the forms thereof shown in the drawing. It may, for instance, be applied to thermostatic devices which use a gas filling instead of a liquid filling.

What is claimed is:

In a thermostatic device, a cylindrical container adapted to be subjected to temperature changes, a capillary tube connected to said container and extending to a pressur responsive device, an ex pansible and contractible liquid filling said container and tube, a cylindrical capsule disposed inside said container with its axis in coincidence with the axis of the container and with its side and end walls substantially uniformly spaced from the walls of the container, said capsule sealed against the entrance of said liquid and being expandible and contractible lengthwise throughout the whole operative range of pressure changes in the liquid, and a coiled spring surrounding said capsule to oppose contraction thereof.

WIILHELM NEUSE. 

